Colombian President Juan Manuel Santos' approval rating has plummeted 27 percentage points to its worst since he took office: 21 percent.

That was the finding of a Gallup poll released Wednesday that was done during the week ending Monday as small farmers demanding lower fertilizer prices blocked roads across the Andean nation.

People gathered in Bogota's main square Wednesday night to bang pots during a rally to support the farmers and chant against the government. Last week, a peaceful protest in the capital of Bogota supporting the farmers devolved into rioting in which two people were killed.

A June Gallup poll gave Santos 48 percent approval.

Both polls queried 1,200 people by phone in five cities and had an error margin of three percentage points.

Gallup director Jorge Londono said the last Colombian president with such low approval ratings was Andres Pastrana in 1999.